This application claims the benefit of German patent application DE P 19959195.4, filed Dec. 8, 1999, herein incorporated by reference.
The present invention relates to a device for pivoting a creel of a textile machine, and more particularly to such a creel which holds a bobbin in contact under pressure with a roller during a winding process, wherein the creel is pivotably seated around a pivot axis and connected with a lifting device by means of which the bobbin and the roller can be selectively separated.
Devices for pivoting a creel are known in various embodiments in connection with textile machines which produce cheeses. For example, German Patent Publication DE 198 17 363 A1 describes a pivotably seated creel of a textile machine which receives a cheese frictionally driven by a drive roller which is connected with a means for generating rotational torque. The contact pressure between the cheese held by the creel and the drive roller is controlled by means of a stepping motor, which can be angularly displaced such that the pressure distribution is matched to the build-up of the bobbin. At the end of bobbin winding, the creel with the full cheese is pivoted into a bobbin removal position by means of a rotating movement generated by the stepping motor. Lifting of the cheese by pivoting the creel with the stepping motor breaks the contact between the cheese and the drive roller.
The winding process is interrupted during bobbin changes, cop changes, and also following yarn breaks. To shorten the length of the interruption it is customary to brake the rotational movement of the cheese. If braking occurs while there is still contact between the cheese and the drive roller, damage to the yarn and errors in the yarn position on the surface of the cheese occur. Even with a free run-out of a cheese resting against the drive roller, but without breaking the contact between the cheese and the drive roller, it is possible that damage to the yarn or the bobbin can occur with yarn of particularly fine count or delicate yarns when there are considerably different surface speeds of the cheese and the drive roller. The faster the contact between the cheese and the drive roller is broken by separating the cheese from the drive roller at a yarn interruption, for example in the case of a yarn break, the less will be the danger that the yarn end is worked into the surface of the cheese by the drive roller which makes it considerably more difficult or even prevents the grasping of the upper yarn by a suction nozzle during the subsequent yarn joining and restart process.
A lifting device of the type over which the present invention seeks to improve is known from German Letters Patent 868 867, which is operative in case of a yarn break to effect an abrupt lifting of the bobbin from the drive drum by means of a creel in the form of a bobbin carrier frame. The extensive and space-limiting design of the rod linkages is disadvantageous in this device. Since such rod linkages must be provided for the lifting device at each winding head in order to make possible the desired rapid lifting of the creel, a very large structural outlay is required for a bobbin winding machine having a plurality of winding heads. The structural space thusly required at each winding head uses space which is only available at the winding heads to a limited degree and which might be needed for the installation and function of further desired or required arrangements. Moreover, the winding head described in German Letters Patent 868 867 can only be manually restarted. The creel is pivotable around an axis, but the lifting device acts on the creel far outside of this pivot point and only permits a very limited pivot range of the creel.
It is not possible with any of the above mentioned devices to dependably break the contact between the cheese and the drive roller in case of a power failure. The above described deficiencies occurring because of the different surface speeds of the drive roller and the bobbin cannot be avoided by means of the known devices.
It is accordingly an object of the present invention to provide an improved pivoting device for a creel to address the aforementioned deficiencies of the known creel lifting devices.
Briefly summarized, the present invention provides, in combination, a textile machine creel for holding a bobbin, e.g., a cheese, in driven surface contact with a drive roller during a winding process and a device for abruptly pivoting the creel out of contact with the drive roller. In accordance with the present invention, the creel comprises a shaft defining a pivot axis about which the creel is selectively moveable relative to the drive roller, and the pivoting device comprises a lever fixedly connected with the shaft for integral movement therewith. A holding element is disposed in a fixed position relative to the shaft, and an arresting element extends between the shaft and the holding element for connection alternately with the shaft or the holding element. An energy storage device is operative when the arresting element is coupled with the shaft for storing potential energy and is operative to release the stored potential energy when the arresting element is coupled with the holding element for abruptly moving the lever to the arresting element for pivoting the shaft.
The invention is distinguished by requiring only little outlay of expense. The transfer of the pivot movement takes place simply and advantageously via the shaft which forms a common pivot axis for the creel and the lever. The contact between the cheese and the drive roller is cancelled without delay and abruptly in case of a current failure, but the device can also be used for breaking contact by separating the cheese and the drive roller in case of a yarn break or a cleaning cut. The present invention also does not hinder the pivoting of the creel over a large pivot range into a position suitable for removing full cheeses.
The energy storage device is preferably embodied as a helical spring acting on the lever and the arresting element, without any further elements for transferring force to the energy storage device being necessary. Use of a helical spring entails particularly low material costs as well as a low assembly outlay, and little structural space is required. In contrast to devices wherein a pneumatic cylinder is charged with compressed air for breaking the contact between the bobbin and the drive roller, a helical spring offers the advantage that in case of a power failure it is not necessary to make compressed air available for the operation of the device in accordance with the invention. However, in the case of performing a contact break in pneumatically operated systems, the demand for compressed air occurring simultaneously at many work stations in case of a power failure can endanger the operational dependability.
A holding element embodied as a toothed segment with teeth on its interior permits an assured fixation of the arresting element which is simple to perform at any moment during the winding process, and therefore also with any bobbin diameter. The arresting element has a piston-and-cylinder lifting assembly for performing the processes of both coupling and uncoupling the arresting element. The fixation of the arresting element by the coupling thereof with the holding element, which is firmly connected with the machine frame, is performed by the movement of the piston rod in the cylinder in the direction toward the holding element. This movement simultaneously causes the uncoupling of the arresting element from the shaft. To uncouple the arresting element from the holding element, the piston rod is moved in the cylinder in the opposite direction. Besides canceling the fixation of the arresting element, the movement of the piston rod away from the holding element toward the shaft causes a coupling of the arresting element with the shaft so as to be fixed therewith against relative rotation. Thus, the coupling processes, as well as the uncoupling processes, are provided by the movement of a single structural element. The mass to be moved and the lifting travel of the piston rod are very small. Thus, it is possible to perform such coupling and uncoupling particularly rapidly and abruptly.
In a preferred embodiment, the shaft, and therefore the creel, are connected with a drive element by means of which the creel can be pivoted in both directions. Potential energy can be supplied to the energy storage element by means of a pivoting movement performed by the drive element, wherein the cheese moves toward the drive roller. The drive element is advantageously designed as a stepping motor, which can be displaced in predetermined angular steps. Stepping motors of this type require little space and are manufactured in large numbers. The use of a stepping motor as the drive element constitutes a simple and cost-effective attainment of the object of the invention. It is possible to omit an additional drive element for moving the lifting device if an existing stepping motor, which can be employed for displacing the creel, is used.
Thus, the drive element can be used for several functions in connection with the subject of the invention. Pivoting the cheese, or the empty bobbin, into the winding position for the winding process can be accomplished with the drive element. Simultaneously with this movement the energy storage device can be charged. During the winding process the contact pressure between the cheese and the drive roller can be controlled by means of the drive element in such a way that the pressure distribution is matched to the build-up of the bobbin. The drive element can perform the additional function of pivoting the creel, even over a large pivot range, into a removal position for full cheeses.
An arresting element which is designed in the shape of a lever is compact and saves space and is well suited for receiving the piston-and-cylinder lifting assembly. Once the arresting element has been coupled with the shaft in a manner fixed against relative rotation, the imaginary center lines of the lever and the arresting element preferably form an angle between about 10 degrees and about 90 degrees, in particular approximately 45 degrees. In this manner, it is possible, following the uncoupling of the arresting element, to create the pivoting movement by means of the release of energy from the energy storage device, which cancels the contact between the bobbin and the roller, particularly effectively via the lever.
The device in accordance with the invention represents a compact, space-saving and cost-effective attainment of the object of the invention. The desired cancellation of contact between the roller and the cheese in case of a power failure can be accomplished rapidly and dependably by means of the device, and in this way it is possible to prevent interference with grasping of a broken or cut upper yarn end for performing a yarn joining operation, as well as to prevent damage to the yarn and yarn positioning errors. The function can be performed in case of a power failure, but also when the compressed air supply fails. Besides triggering the separation of the bobbin and the drive roller, it is also possible to automatically perform the restart of the winding station. Thus, it is possible to reduce down time and to increase the productivity of the winding station or of the textile machine.
Further details, features and advantages of the present invention will be explained by means of an exemplary embodiment represented in the drawings.